Table 1. Demographic background of the 80,270 participants.
| Variables | Missing data (%) | Mean (SD) or N (%) | |||
|---|---|---|---|---|---|
| Maternal demographics | |||||
| Maternal age | 11 (0.0) | 31.1 (5.0) | |||
| Maternal height | 10 (0.0) | 158.1 (5.3) | |||
| Pre-pregnancy maternal weight | 32 (0.0) | 53.0 (8.7) | |||
| Maternal weight gain | 613 (0.8) | 10.3 (4.0) | |||
| Primaparae | 344 (0.4) | 46,034 (57.3) | |||
| ART pregnancy | 308 (0.4) | 2,554 (3.2) | |||
| Pre-existing hypertension | 308 (0.4) | 342 (0.4) | |||
| Pre-existing diabetes | 308 (0.4) | 158 (0.2) | |||
| Maternal allergic history | 308 (0.4) | 40,834 (51.1) | |||
| Maternal current smoking | 846 (1.1) | 3,243 (4.1) | |||
| Paternal current smoking | 1,836 (2.3) | 35,916 (45.8) | |||
| Cesarean section | 138 (0.2) | 14,571 (18.2) | |||
| Maternal education | 281 (0.4) | ||||
| Junior High School | 3,372 (4.2) | ||||
| Senior High School | 58,802 (73.3) | ||||
| University | 17,815 (22.2) | ||||
| Annual household income | 5,243 (6.5) | ||||
| < 4 million-yen | 29,630 (36.9) | ||||
| ≥ 4 and < 6 million-yen | 25,074 (31.2) | ||||
| ≥ 6 million-yen | 20,323 (25.3) | ||||
| Folic acid supplementation | 517 (0.6) | 39650 (49.4) | |||
| During pregnancy | |||||
| Breastfeeding at one month after delivery | 2203 (2.7) | ||||
| Breastfeeding only | 42157 (52.5) | ||||
| Mixed feeding | 33039 (41.2) | ||||
| Artificial milk feeding | 2871 (3.6) | ||||
| Children’s demographics | |||||
| Allergic disorder at one year of age | |||||
| Asthma | 0 (0.0) | 2,027 (2.5) | |||
| Wheeze | 438 (0.5) | 15,617 (19.6) | |||
| Atopic dermatitis | 0 (0.0) | 3,477 (4.3) | |||
| Eczema | 387 (0.5) | 14,929 (18.7) | |||
| Food allergy | 0 (0.0) | 13,801 (17.2) | |||
| Any allergy | 311 (0.4) | 25,028 (31.3) | |||
| Infant sex | 16 (0.0) | ||||
| Male | 41,003 (51.1) | ||||
| Female | 39,251 (48.9) | ||||